Filter means with a segmental construction

ABSTRACT

The invention relates to a filter means for filtering gases, liquids or similar filtering media, preferably for process engineering plants, e.g. those for the foods and drinks industry, such as for compressed air preparation, particularly in sterile operation, optionally under overpressure conditions and/or at high temperatures, in which there is a segmental construction, formed by essentially circular filter elements, against which a flow can take place from the inside and outside, together with interposed, disk-shaped filter material and in which the entire edge area of the filter material sealingly cooperates with the filter elements.

The present invention relates to a filter means for filtering gases,liquids or similar filtering media, preferably for process engineeringplants, e.g. those of the foods and drinks industries, such as forcompressed air preparation, particularly in sterile operation,optionally under overpressure conditions and/or at high temperatures.

Very high demands are made on filter means for a field of use of theaforementioned type. Apart from an assured complete fulfilment of thenecessary filtering requirements, it is necessary to ensure a reliable,troublefree operation, because a failure of the filter means not onlyleads to unusable products, but also to enormous stoppage losses in theplants in question.

Particularly during the production of foods and drinks, such as inbreweries, apart from the above requirements, it is frequently alsonecessary to ensure that the filtering agents are absolutely sterileafter passing through the filter means. If the filter means fails insterile operation, which is not always immediately detectable,considerable production quantities can be rendered unusable.

In general, such filter means have a very wide range of application andapart from use for filtering out fuels from gases, e.g. for separatingoil from compressed air, (oil separators), they are used e.g. fordeionizing water, removing microorganisms from drinks, nutrient brothsfrom fermenters and the like. Such filter means must withstandtemperatures up to 200° C. and in part up to 300° C. and pressures inthe range of 16 to 20 or even 30 bar. They must also not fail if thedesign capacity is under certain circumstances briefly exceeded, even bydouble or even treble.

A filter means of the aforementioned type and for the aforementionedpurposes is e.g. described in DE-OS No. 3,125,001. As can be gatheredtherefrom, such a filter means essentially comprises a tubular, normallyvertically positioned filter material, which is held in an inner andouter tube, which is e.g. constructed in screen-like manner. At the topand bottom, the filter material, which is also referred to as filtercartridge, is held by a cover plate. In order to ensure a reliable sealbetween the filter material and the cover plate, for reliably preventingfilter perforation, the filter material is bonded to both the upper andlower cover plate (cf e.g. U.S. Pat. No. 4,157,968). In additiona, it isalso known to weld the filter cartridges to the corresponding covers.Replacement is necessary at regular intervals because after a certainoperating period there is increasing clogging of the filter material andthe filtering capacity decreases, or an unacceptably high pressure dropoccurs. As a result of the aforementioned bonding or welding, in thecase of the known filter means, it is necessary to replace the completefilter element, including the upper and lower covers, as well as theinner and outer tubes supporting the filter material, said partsgenerally being made from a high-grade material, particularly stainlesssteel. Quite apart from a not inconsiderable labour time, such areplacement involves considerable costs, because the parts to bereplaced in the known filter means are made from a very high-gradematerial, e.g. stainless steel, so that they have a very value comparedwith the actual part which is subject to wear, i.e. the filter material.However, for the aforementioned fields of application, only theaforementioned filter means have hitherto been used. Onlly in the motorvehicle field is an air filter known, which comprises a segmentallyconstructed filter element, in which filter material in disk-like formis maintained in spaced manner by spacer rings (cf German Patent No.681,303). These spacer rings in each case comprise tube portions withdifferent diameters, having alternatley inwardly and outwardly directedwebs. The spacer rings are superimposed in a regularly alternatingsequence with interposed filter material. Thus, air sucked in itsdeflected upwards or downwards by the spacer ring with the outwardlydirected webs and in the vicinity of the spacer ring with the inwardlydirected webs is sucked into the clean air line after the air has inthis way been forced through the interposed filter material. Althoughthis known filter means may well be satisfactory for use in cleaning theintake air for internal combustion engines, it is not suitable for theuses intended for the aforementioned filter means according to theinvention. The spacer rings essentially only space the filter material,but do not lead to an adequate sealing of said material, which wouldpermit a use of such filter means e.g. under sterile operatingconditions. In the superimposed sequence between the spacer rings, thereare in each case quadrant-shaped regions on the inside and outside, inwhich the filter material only rsts on one side on a spacer ring, but isnot held in a sealing manner. There is no difficulty in bypasses orfilter passages occurring here, particularly if, which is not providedin the filter means, the filtering medium is a liquid. Up to now, such afilter means has only been known as an air filter for internalcombustion engines.

In view of the aforemention shortcomings of the known filter means ofthe present type, the problem of the present invention is to provide afilter means for filtering gases, liquids and similar filtering media,preferably for processing plants and the like which, without restrictionwith regards to the field of use, is easier to maintain and regenerate,whilst at least having the same operational reliability and filteringcapacity.

Accordingn to the invention, this problem is solved by a filter meanscharacterized by a segmental construction formed by substantiallycircuilar filter elements, against which a flow can take place from theinside and outside, together with interposed, disk-shaped filtermaterial. The invention also teaches a filter means, which ischaracterized in that its entire edge area, the filter materialsealingly cooperates with the filter elements.

Thus, the invention has recognised that the aforementioned filter meanshaving a segmental construction and known from the motor vehicle fieldis fundamentally also suitable for the uses under consideration here. Asa result of the teaching of sealing the filter material over its entireedge area with or with respect to the circular filter elements, it ispossible to use this filter means in fields where it has hitherto onlybeen possible to use filter means having filter cartridges.

As a development of the aforementioned teaching, the invention alsoteaches that each filter element has an inflow port and an outflow port,which are in each case constructed in an inner wall or an outer wall ofthe filter element. In accordance with the known "cartridge" filtermeans, the filter means according to the invention either has anincident flow from the outside, the "clean" medium then being drawn fromthe interior of the filter means, whose substantially double-tubeconstruction is retained. In the case of the reverse flow direction, thefiltering medium flows from the inside to the outside. With respect tothe presently described flow direction, the term inner wall is used todefine the terminating region of the filter element towards the inside,i.e. in the case of the known double-tube construction the areacorresponding to the inner tube. In the same way, the outer walldesignates the area coinciding with the larger diameter tube. The inflowport in the outer wall or the outflow port in the inner wall leads ineach case to a clearly defined "chamber" being formed, into which ineach case the filtering medium flows from the outside, is deflected andthen passes through a filter medium above or below it. A thus formedchamber, which can have four outflow ports or inflow ports distributedover the circumference, is provided at the top and bottom with inner andouter through sealing edges or strips, against which the filter elementscan be sealingly pressed so that it is not possible to circumvent thefilter.

According to a further development, the invention teaches positioningupstream of the filter material in the flow direction of the filteringmedium at least one screen or the like. This can fundamentally beobtained in that the screen is constructed in one piece with the filtermaterial. However, in certain cases, the filter material per se maysuffice, so that a screen is not then necessary.

If it is sufficient to have a screen arranged in the flow direction infront of the filter medium of holding back or filtering out coarseconstitutents there, it can still be appropriate for the filter materialto be followed by a screen. As a result, the filter means can be used ina universal manner, because there is always a screen upstream of thefilter material, independently of the flow direction. Such anarrangement also ensures that if the filter medium should tear, which isextremely rare, but still cannot be completely excluded, if extremeconditions act on the filter means as a result of a fault in the plant,no filter material can reach the "clean" side, because it is reliablyheld back by the screen provided behind the filter material in the flowdirection.

The filter element of a filter means according to the invention canfundamentally be constructed in one piece, but only for as long as onescreen is provided. From the manufacturing standpoint, it is recommendedto produce the filter element in the form of an inner ring and an outerring, which are interconnected by the screen. For this purpose, theinner and outer edges of the screen can be welded or bonded to the innerand outer ring. Particularly if a screen is to be arranged upstream anddownstream of the filter medium, it is recommended that the screen bedetachably connected with the inner and outer ring, e.g. by a screwcoupling. Fastening e.g. by attachment screws could also beadvantageous.

However, a special development of the inventive teaching is directed atlockably holding a screen in the outer ring. The screen, which isusually an extensible steel body, is pressed in this case into a lockingslot in the outer ring and then rests on a corresponding surface or acorresponding all-round shoulder of the inner ring. In the case of twoscreens fixed in parallel spaced manner in the outer ring, it ispossible to secure the inner ring only by positive engagement.Preferably, the clamping spacing of the screen is a little smaller inthe outer ring than in the inner ring or then the spacing of theall-round shoulders of the inner ring, so that the screenssimultaneously rest under pressure on the inner ring. Such aconstruction firstly leads to a very easy assemblability of theapparatus, because additional welding, bonding or screwing isunnecessary. In addition, between the inner and outer rings, there is acertain relative elasticity and displaceability, without the risk of thejoining points, e.g. welding spots breaking up. This elasticity is ofgreat significance for a reliable tight seal between the filter elementsand the interposed filter media, as will be described in greater detailhereinafter.

Preferably, the filter material is also arranged in spaced manner withrespect to the screens. Thus, to a limited extent the filter materialcan "work", so as to have space for expansions linked with temperaturefluctuations.

It is of considerable importance for the sealing of the filter means,the sealing cooperation of the filter elements with the filter materialis that with respect to all the filter elements and all the inner andouter rings thereof, the necessary pressure always prevails betweenadjacent filter elements, in order to ensure the sealing pressure of thefilter material. Particularly if relatively thin filter material isused, which is also relatively slightly extensible, there can be aconsiderable reduction in the pressure between the outer or inner ringsof the filter elements as a result of settling phenomena. To obviatethis, the invention further teaches supporting at least one segment,preferably an end segment of the filter means, against the followingsegments by means of a rubber bead, e.g. an O-ring or a rubber bead withan upper circular cross-section and a lower rectangular cross-sectionfor fitting in a slot. If settling phenomena occur between furthersegments, the mounting support of the segments can follow, as in thecase of a compression spring and the pressure is maintainedsubstantially unchanged. To the extent that the segments, as taughthereinbefore, comprise inner and outer rings, the inner and outer ringat the end segment preferably has such a rubber bead.

Quite apart from the importance of compensating settling phenomena,O-rings or rubber beads, etc can also be advantageous if the filtermaterial is inelastic, such as e.g. a ceramic material. It is thenrecommended to place such O-rings or rubber beads between the filtermaterial and the filter element, i.e. between the inner and outer rings.

It is also advantageous for holding together the filter elements tobrace the upper and lower mounting supports of said elements withrespect to one another by using a tie bolt. The tie bolt can e.g. be alongitudinal screw passed through the centre of the filter means andcoinciding with the axis of the latter, whilst bringing about areciprocal bracing of the upper and lower mounting supports for thesegment.

A filter means according to the invention as described hereinbefore canfundamentally be operated with different filter materials. As the flowrate is also a function of the filter surface available, it isadvantageous to house the maximum number of filter segments in a givenarea. An economic utilization of this area is aided by the relativelythin filter elements. To satisfy this requirement, the invention furtherteaches the use of plastic membranes as the filter material in filtermeans of the present type, particularly in a filter means with one ormore of the aforementioned features. The starting material for suchmembranes is e.g. marketed under the trade mark GORE-TEX.

Such a filter material comprises a membrane, which is filter-active anda support material connected thereto. As it is relatively easy to passthrough the support material, which also applies with respect to theconstituents to be filtered, which have just been held back in thefilter-active membrane, it is necessary to fit such membranes in aspecific manner in such a filter means, namely in such a way that thefiltering medium initially flows through the filter-active membrane andthen the support materials. Otherwise, the support material could leadto a "short-circuit", i.e. substantially unfiltered filtering mediumreaching the "clean" side.

However, a special teaching of the invention is directed at using an atleast three-layer membrane element, which correspondingly comprises afilter-active membrane, followed by a support layer and then by afurther filter-active membrane. No matter the way in which such amembrane is fitted, a "short-circuit" cannot occur therewith.

It can also be advantageous to use a four-layer membrane element, whichis formed from two two-layer membrane elements, which are interconnectedin such a way that the support layers are in each case adjacent to oneanother. A particularly stable membrane element is then produced fromthe starting material.

As stated hereinbefore, it is of great significance for a filter meansof the aforementioned type for it to be completely tight, i.e. excludingthe filtering medium from in any way passing through the filter meanswithout filtering, i.e. bypassing the filter material. It is ofparticular importance that the filter material, particularly in the caseof a filter means as described hereinbefore, is held in a sealing mannerbetween the filter elements, i.e. between the outer and inner rings.This can fundamentally be aided in that the outer and inner edges of thefilter elements are surrounded with a sealing border.

Particular preference is given to providing the filter element with aninner and an outer bead at the time of production by a suitable pressingor shaping action.

Further details of the invention can be gathered from the subclaims, aswell as the following description of embodiments relative to theattached drawings, wherein show:

FIG. 1 a basic representation of a filter means according to theinvention.

FIG. 2 two filter elements of a filter means according to the invention,as well as an interposed membrane element on a larger scale.

FIG. 3 in section, a larger-scale, half-side representation of amembrane element according to the invention.

FIG. 4 an alternative embodiment of a filter element according to theinvention.

FIG. 5 a further alternative filter element, which is open to the insideand closed to the outside.

FIG. 6 a plan view of a filter element according to FIGS. 4 and 5 withsupport walls.

FIG. 7 a further alternative filter element with slot-like openings inthe end faces.

FIG. 8 a diagrammatic representation of two superimposed filterelements, in an alternative embodimient, with interposed filter materialand annular sealing elements.

FIG. 9 a further embodiment of an alternative filter element, with anannular bead parallel to the inner and outer walls on one end face andwith an annular depression parallel to the inner and outer walls of theother end face.

FIG. 10 a further alternative embodiment of filter elements, some onlyhaving bead-like projections, whilst the others only have depressions,in sectional form.

FIG. 11 another alternative construction of a filter element, abead-like, annular sealing element and a groove-like sealing elementbeing provided on the particular end face of the filter element, insection.

FIG. 12 a plan view of an alternative filter material set.

FIG. 13 a cross-section along line A--A in FIG. 12.

FIG. 14 another alternative embodiment of a filter material set, a metalscreen being used as the filter material sheet and sectioned along lineA--A in FIG. 12.

FIG. 15 a multilayer filter material set, sectioned along line A--A inFIG. 12.

FIG. 16 a filter material set, in which the filter material is fixed bymeans of screws to multilayer borders, sectioned along line A--A in FIG.12.

FIG. 17 an embodiment, in which the filter material is fixed in twoborders by the application of pressure, sectioned along line A--A inFIG. 12.

FIG. 18 another alternative embodiment in which the border or borders donot embrace the edge of the filter material set, sectioned along lineA--A in FIG. 12.

FIG. 19 a plan view of the filter material set of FIG. 18.

FIG. 20 a use of a filter material set in a filter means.

What is shown and described is a filter means 10 for filtering gases,liquids or similar filtering media in process engineering plants, as hasbeen described hereinbefore.

FIG. 1 shows the filter means 10, the filtering medium passing throughsupply line 12 into filter means 10, then passes through the filterelements 1 and is then returned to the plant of which filter means 10 isone element through the discharge line 14. For illustration purposes,filter material 2 is shown on a much larger scale in the filter means 10shown in FIG. 1. As can be seen, the filter elements 1 are partly closedtowards the inside, i.e. towards the supply pipe 12 and in part have anopening to the latter.

In the embodiment shown in FIG. 1, the filtering medium flows throughthe openings of the filter elements 1 open towards supply pipe 12 andthen, with a flow deflection of about 90° flows through the filtermaterial 2 and accompanied by a further flow deflection of substantially90° passes through further elements 1, which are open towards theoutside, i.e. towards the clean medium area 16. As FIG. 1 also shows,the filter elements 1 are secured by upper or lower borders orprotective covers 28, 30.

Although reference has previously been made to the filtering mediumflowing from supply pipe 12 into the particular filter elements 1, itcan be more clearly seen that supply pipe 12 issues into a filter innerline 18, which need not be a line in the physical sense and can insteadbe formed by filter elements open or not open towards the same.

As can be seen in FIG. 2, the filter means 10 according to the inventionis constructed segmentally, namely by substantially circular filterelements 1, which comprise an outer ring 9 and an inner ring 8. In theembodiment of FIG. 2, outer ring 9 and inner ring 8 are held together byscreens 7, which are positively engaged in the outer ring 9. Due to thefact that the screens 7 rest on the all-round shoulders 51, 52 of innerring 8, the complete filter element 1 comprising outer ring 9, the twoscreens 7 and the inner ring 8 is held together.

As can also be seen in FIG. 2, the inflow ports 3 or outflow ports 4 areconstructed in bore-like manner in the outer ring or inner ring. Thus,all-round sealing faces 53, 54 can be formed on outer ring 9 and also oninner ring 8 and the filter material 2 rests thereon. In this way, thefilter material 2 is held in a completely sealing manner between the twofilter elements 1, which in each case have corresponding sealing faces53, 54 on their underside.

FIG. 2 only shows two outflow ports 4 or inflow ports 3, but preferablya filter element 1 has four outflow ports 4 or inflow ports 3.

FIG. 2 also shows that the filter material 2 resting on the sealing face53, 54 is positioned in a spaced manner with respect to the upstream anddownstream screens 6 when the filter means is assembled and theaforementioned advantages are consequently obtained.

What is not shown is that according to a further embodiment of theinvention, an end filter element 1 can be provided with a rubber bead oran O-ring, so that said filter element cooperates with the filterelement above it or below it. Although this rubber bead canfundamentally be provided in sealing face 53 and sealing face 54, it isalso possible to construct the rubber bead on inner ring 8 in contactface 55 and in outer ring 9 in an outer region of sealing face 53, sothat the positioning of filter material 2 on sealing faces 53, 54 is notdisturbed. As a result of this rubber bead or this O-ring settlingphenomena in filter means 1 are prevented and in certain circumstances,they could lead to leaks due to the reduction in pressure between theindividual filter elements 1.

FIG. 3 shows half a filter membrane in cross-section and according tothe invention this is used as filter material 2. This filter membrane ispreferably a PTFE membrane and comprises three or four layers, whereofthe central or the two central layers are support material layers,whilst the outer layers exert the actual filtering action. This has beendescribed in greater detail hereinbefore. As is shown in FIG. 3, thefilter material 2 or the filter membrane has an outer all-round sealingbead 56 and a corresponding inner all-round sealing bead 57, whoseadvantages have been described hereinbefore.

FIGS. 4 to 11 show alternative embodiments of the filter element 1,which will also be called filter segments hereinafter. As has beenstated, for a filter means 10 according to the invention, two differentfilter elements or segments 1 are required.

The filter segment 26 of a first type shown in FIG. 4 is provided withopenings toward the clean medium area 16 and they can have a randomshape which is compatible with the stability of the filter segment.These openings permit a free outflow of cleaned material, which flowsfrom the filter material into the outwardly open filter segment throughthe openings in the end face of filter segment 24 (FIG. 5). The secondtype of filter segment 24 is inwardly provided with openings, takes upthe uncleaned material and passes it through openings in its end facesinto the filter material 2. As this filter segment 24 is constantlyexposed to contamination, it can prove necessary to separately cleanthese elements, or replace them or make from a material which isinsensitive to the contamination. The outwardly open filter segments mayrequires less cleaning and can be made from a less expensive and lessresistant material.

It is desirable for absorbing the pressure exerted on the filtersegments to provide radial support walls 32 in the individual segments,which serve to prevent deformation of the segments in the direction ofthe main filter axis, which could cause leaks. The number of radialsupport walls 32 is not very critical, but for reasons of increasedmechanical stressing, it can be advantageous to provide many moresupport walls than are shown in FIG. 6.

FIG. 7 shows a further possible construction of the openings in the endfaces of the filter segments in the form of radial slots, which can bedesirable for manufacturing, material or resistance reasons. The endfaces of the filter segments can obviously also be provided withcircular openings or openings of any other shape, the only limit placedon the size and shape of the openings being based on the stability ofthe filter elements.

It is necessary to seal filter material 2 against the inside and outsideline. FIG. 8 shows a preferred embodiment in which annular beads areformed in both types of filter segments 24, 26 and in them can be placedring-like sealing elements 38, between which the filter material 2 isintroduced or inserted in sheet or disk form. This sealing element canbe made e.g. of Teflon, silicone, rubber, etc, as a function of thematerials to be cleaned.

FIG. 8 shows a preferred embodiment of the seal, whereby the filtersegments have bead-like, annular depressions on one end face, whilst thesegment surface has protuberances which on compressing the two filtersegments engage with one another in such a way that a seal is achievedbetween the depression and the bead and the filter material 20 embeddedbetween the filter segments 24, 26 is sealed against the inner and outerline.

FIG. 10 shows a filter, in which the material to be cleaned flows fromthe outside to the inside through the filter and in which equivalentparts are given the same reference numerals.

To give an idea of rough dimensions, but which are not intended torestrict the scope of the invention, the internal diameter of the filterinner line of conventional tubular filters is between 3 and 15cm, whilstthe length of conventional tubular filters can be between 2 and 100cm.The embodiment according to the invention is not restricted to thesedimensions.

An example of filter elements as shown in FIG. 1 are oil separators,water separators, ion exchangers and the like.

The embodiment shown in FIG. 10 is e.g. suitable for sterile filters.

FIGS. 12 to 20 show different embodiments of a membrane element or afilter material set.

As shown in FIG. 12, a sealing border is provided for sealing a membraneelement or a filter material disk on the edge are of a circular filtermaterial disk and as shown in FIGS. 13 or 14, it is made from a materialdiffering from that of the filter material sheet and is preferably anelastic material, such as rubber, plastic, etc. By applying pressure atright angles to the main extension direction of the filter material aseal is obtained by compressing the material.

If planar surfaces are available as sealing surfaces for surface sealingpurposes, then, as shown in FIG. 13, a rectangular or parallelepipedicconstruction of the sealing borders 114 or 116 can be advantageous.

However, it can be advantageous to have a circular, elliptical or roundcross-section of such borders 116, 114, as shown in FIG. 1 relative tothe example of a surface filter represented as a screen.

FIG. 15 shows an embodiment, in which different layers are reinforced byintermediate back cloth and are then fixed by polymerized-on borders.There is an alternation between back cloth layers 108 on the one handand filter fleece 20 and filter resin 22 on the other.

As shown in FIG. 16, it can be useful for particularly high pressures,if a tear-resistant filter material sheet is fixed by known mechanicalfixing devices. In this case, screws 118 are placed through the filtermaterial sheet 100 and a metal bordering part 120 for fixing said sheet.A further elastic layer 122 surrounds the metal core, in order to ensurea better seal. As a result of such a fixing of the filter materialsheet, a puncturing of the filter is prevented and a better fixingthereof ensured.

FIG. 17 shows a particularly preferred embodiment of the filter materialset according to the invention, in which a loose filter materialprovided at the top and bottom with a back cloth is held by the clampingaction of two covers 110.

FIGS. 18 and 19 show further embodiments of a filter material accordingto the invention, in which the borders are fitted in spaced manner fromthe outer most edge of the filter material disks. This maintaining ofthe spacing can e.g. be necessary, if such an application permits abetter penetration of the material with the sealing or borderingmaterial or a better mechanical strength of the sealing connection canbe obtained, particularly with respect to pressure action.

FIG. 20 relates to the use of the filter material set according to theinvention in a filter means for filtering gases and liquides. The mediumto be filtered passes through the upper filter segment in FIG. 20through open side walls of the filter segment disk, passes through theperforation in the segment bottom into the underlying filter materialset 100 and leaves it in filtered form in another identical filtersegment, which is open towards the filter inner line and closed towardsthe filter outer line and also has perforations in its two end wallstowards the filter inner line. Such filter arrangements can be stackedat random levels, the filter material set must be sealed against thefilter segments in order to achieve a satisfactory filtering action.

It is also pointed out that in FIG. 17 reference numeral 112 designatesa surface filtration filter material sheet.

The features of the invention disclosed in the above description,drawings and claims can be essential for the realisation of thedifferent embodiments of the invention either singly or in randomcombination.

The disclosure of the enclosed copies of the Applicant's earlierapplication "enclosure 1" and "enclosure 2" is fully incorporated intothe description of the present invention.

I claim:
 1. A filter for filtering gases, liquids and similar media,comprising a segmental construction formed by: at least two circularfilter elements (1) against which a flow can take place from the insideand outside and at least one disk-shaped filter materila (2); each saidfilter element comprising an inner ring, an outer ring, at least onemember connecting said rings, and a fluid port in one of said rings;each said disk-shaped filter material being positioned intermediate twoadjacent ones of said filter elements and being supported by said twoadjacent filter elements; said filter material having substantially itsentire edge area in sealing cooperation with the adjacent filterelements (1); and said filter material and said adjacent filter elementsdefining a flow path for a medium to be filtered in which said mediumenters through said fluid port in the inner ring or the outer ring ofone of said adjacent filter elements, passes through said filtermaterial between said adjacent filter elements, and exits through saidfluid port in the inner ring or the outer ring of a second one of saidadjacent filter elements.
 2. A filter according to claim 1 furthercharacterized in that segments (24, 26) of the filter element areannular and have support walls (32) running radially to the axis of theinner line (18) and at right angles to end faces (34) of the segments.3. A filter according to claim 2 further characterized in that thefilter elements are each provided on the end faces with two beadsparallel to the inner and outer walls (27, 29) of the segments.
 4. Afilter according to claim 3 characterized in that the filter elements(24, 26) each have two annular depressions on the end faces (34), saiddepressions running parallel to the outer wall (27) and the inner wall(29) of the segment and being constructed to sealingly engage with thebead of an adjacent filter element.
 5. A filter according to claim 2further characterized in that at leat one said end face (34) hasopenings in the form of at least one of holes, slots, and screens.
 6. Afilter according to claim 1 wherein said filter material comprisesplastic membranes.
 7. A filter according to claim 6 wherein said plasticmembranes are PTFE membranes.
 8. A filter according to claim 6 whereineach siad membrane has at least two layers.
 9. A filter according toclaim 6 wherein each said membrane has at least three layers.
 10. Afilter according to claim 1 further characterized in that said at leastone member connecting said rings comprises a screen (7) locked in atleast one of the outer ring (9) and the inner ring (8).
 11. A filteraccording to claim 10 further characterized in that each said filtermaterial (2) is arranged in spaced manner with respect to the screen(7).
 12. A filter according to claim 1 characterized in that at leastone said filter element is supported against an adjacent filter element(1) by means of at least one of a rubber bead and an O-ring.
 13. Afilter according to claim 12 further characterized in that each saidfilter element ring has at least one of said rubber bead and saidO-ring.
 14. A filter according to claim 1 further characterized in thatthe filter material is formed from a non-reusable material.
 15. A filteraccording to claim 14 wherein the filter material is selected from thegroup consisting of paper, cellulose, felt, leather, asbestos, sawdust,pumice and titanium dioxide.
 16. A filter according to claim 1 furthercharacterized in that the filter material (2) is a regeneratablematerial.
 17. A filter according to claim 16 wherein the filter materialis selected from the group consisting of glass, Teflon, porcelain,synthetic resin ion exchangers and metal.
 18. A filter according toclaim 1 further characterized in that at least one screen (7) ispositioned upstream of each said disk-shaped filter material in the flowdirection of the medium to be filtered and in that said at least onescreen forms said at least one member connecting said rings in said oneadjacent filter element.
 19. A filter according to claim 1 furthercharacterized in that each said disk-shaped filter material is followedby at least one screen (7) which forms said at least one memberconnecting said rings in said second one of said adjacent filterelements.
 20. A filter according to claim 1 wherein said filter is usedin a process engineering plant for compressed air preparation under atleast one of sterile operating conditions, overpressure conditions andhigh temperature conditions.